1. Field of the Invention
This invention relates to novel aromatic diamines, the polyimide oligomers and the polyimides derived from said diamines and polyimide oligomers. More specifically, this invention relates the novel diamines, the oligomers and the polyimides derived therefrom and to the method of preparing the diamines, polyimide oligomers and the polyimides. The polyimides derived from the aromatic diamines of this invention are characterized as having high glass transition temperatures, good mechanical properties and improved processability in the manufacture of adhesives, electronics and composite materials. The distinction of the novel aromatic diamines of this invention over the prior art resides in the 2,2'- and 2,2',6,6'-substituted biphenyl moieties which exhibit noncoplanar conformation that enhances the solubility of the diamine as well as the processability of the polyimides, while retaining a relatively high glass transition temperature and improved mechanical properties at useful temperature ranges.
The novel aromatic diamines and the polyimides derived therefrom in accordance with this invention can be characterized by the following formula and by the disclosure more specifically set forth herein. ##STR1##